1. Field of the Invention
The present invention relates to a fuel cell module having a power-generating chamber containing solid-oxide fuel cells and a casing enclosing the same.
2. Description of the Related Art
FIG. 26 is a schematic sectional view showing a typical example of a conventional solid-oxide fuel cell module 100 (refer to Japanese Unexamined Patent Publication (Kokai)) No. 2005-123014, Japanese Unexamined Patent Publication (Kokai) No. 2005-158526 and the like).
A metal casing 110, which has a generally rectangular shape and encloses a power-generating chamber 111, is provided with heat exchanger 120a and 120b disposed on four or two side faces. The power-generating chamber 111 includes therein, for example, four rows of cell stacks 80 of fuel cells arranged in a line, reformers 71 each disposed thereabove, and manifolds 72 each attached to the respective cell stacks 80. Each of the manifolds 72 is a fuel gas case. Above the power-generating chamber 111, an oxygen-containing gas chamber 140 is disposed. From the oxygen-containing gas chamber 140, a plurality of oxygen-containing gas introduction tubes 141 extends downward vertically into the power-generating chamber 111. Each of the oxygen-containing gas introduction tubes 141 is disposed between the cell stacks. Between the manifold 72 and a lower wall and between the power-generating chamber 111 and the heat exchanger 120a and 120b, heat insulators 61 and 62 are disposed. Although not shown in FIG. 26, outside of the casing 110 also, heat insulators are appropriately disposed, and further, the entirety thereof is received in an appropriate housing, constituting a fuel cell assembly.
A bottom plate 142 of the oxygen-containing gas chamber 140 is placed on the upper face of the exchanger 120a and 120b and the power-generating chamber 111, and fixed thereto. The periphery of the bottom plate 142 protrudes outward of the casing 110 like a flange. In order to seal the gas, the flange portion of the bottom plate 142 is welded to the casing 110. A member constituting the side faces and the upper face of the oxygen-containing gas chamber 140 is placed on the bottom plate 142 and fixed thereto. The plurality of the oxygen-containing gas introduction tubes 141 are attached to the bottom plate 142.
Referring to FIG. 26, an oxygen-containing gas (for example, air) is taken from the outside. The gas enters the oxygen-containing gas flow path (outer flow path) of the heat exchanger 120a and 120b through the lower wall of the casing 110. Passing through the heat exchanger 120a and 120b from the lower portion toward the upper portion thereof, the gas flows into the oxygen-containing gas chamber 140 (indicated with white arrows). On the other hand, a gas to be reformed (for example, hydrocarbon gas such as city gas) is supplied to the reformers 71 through a reform gas supply tube. The reform gas is reformed into a hydrogen-rich fuel gas by a reforming catalyst and fed to the manifolds 72 through pipes (not shown). Utilizing the oxygen-containing gas supplied from the oxygen-containing gas introduction tubes 141 and the fuel gas supplied from the manifolds 72, a power-generating reaction occurs in the cell stacks 80, and thus, the current is output through an output means (not shown). After the power generating reaction, the waste gas enters waste gas flow paths (inner flow path) in the heat exchanger 120a and 120b from an upper portion of the power-generating chamber 111. Passing therethrough from the upper portion toward the lower portion thereof, the waste gas flows out through the lower wall of the casing 110 (indicated with black arrows). Heat is exchanged by the oxygen-containing gas flow path and the waste gas flow path being disposed adjacent to each other in the heat exchanger 120a and 120b, and thereby the oxygen-containing gas is preheated by the heat of the waste gas.
In the above-described fuel cell module 100, the inside of the power-generating chamber 111 has to be maintained at a high temperature of 700 to 1,000° C. when carrying out power generation.